Leishmania major is one of several Leishmania parasites that, when introduced into a host organism, is the causative agent of leishmaniasis. Leishmania major is a species of the Leishmania tropica complex. Other complexes (comprising species and subspecies) include Leishmania donovani, Leishmania mexicana, and Leishmania viannia. According to the World Health Organization, leishmaniasis is among the most infectious diseases worldwide and is endemic in 88 countries in Africa, Asia, Europe, and in North and South America. It has been estimated that over 12 million people suffer from Leishmanial infections worldwide, where serious public health problems exist particularly in countries such as Iran, Iraq, Afghanistan, Algeria, Brazil, India, Peru, and Syria. Leishmaniasis most commonly manifests itself as either cutaneous (i.e. skin) leishmaniasis (CL) or visceral (i.e. internal organs) leishmaniasis (VL). CL is the most common form of leishmaniasis and is the result of transmission of the parasite Leishmania major via the bite of an infected female phlebotomine sandfly. Symptoms of CL include large skin legions or ulcers on exposed parts of the body, which cause serious disability and permanent scarring.
Methods of treating leishmaniasis have typically been limited to administering pentavalent antimony (SbV) (Sundar et al. (2002) Curr. Opin. Infec. Dis. 15, 593-598). Due to the recent emergence of large-scale resistance to SbV, however, the effectiveness of this treatment is becoming increasingly limited. Furthermore, SbV treatment has several side effects including nausea, vomiting, diarrhea, and convulsions. In addition, HIV co-infection with Leishmania species presents further challenges since such co-infection can dramatically alter the epidemiology, diagnosis, and response of leishmaniasis to therapy (Lee et al. (2003) Int. J. Infect. Dis. 7, 86-93).